Mutations in the Opaque2 (O2) gene of maize (Zea mays L.) improve the nutritional value of maize by reducing the level of zeins in the kernel. The phenotype of o2 grain is controlled by many modifier genes and is therefore strongly dependent on genetic background. We propose two hypotheses to explain differences in phenotypic severity in different genetic backgrounds: (i) Specific genes are differentially (o2 vs. wild‐type) expressed only in certain genotypes, and (ii) A set of genes are differentially expressed in all backgrounds, but the degree of differential expression differs in different backgrounds. To determine the extent to which these two hypotheses contribute to determining the severity of o2 in different genetic backgrounds, we identified transcripts likely to be differentially expressed in several genetic backgrounds by transcript profile comparison of endosperm RNA pools from eight o2 inbred lines and their wild‐type counterparts. The inbred line B46 was identified as having severe o2 phenotypes while the line M14 was identified as having minimal o2 phenotypes. The degree of wild‐type vs. o2 differential expression of transcripts was determined for these two lines. We found that most genes that are downregulated by o2 tend to be differentially expressed to a greater degree in B46 than in M14, while upregulated genes tend to be more highly differentially expressed in one genetic background or the other. Thus, hypothesis one functions more prominently for upregulated genes while hypothesis two functions most prominently for downregulated genes.

Cereal products made from pigmented grains are attractive to consumers. We determined the variability in color, phenolic composition and antioxidant activity (AA) of blue tortillas made from 18 landraces belonging to three blue/purple grained Mexican maize races -Chalqueño (Chal), Elotes Cónicos (Ec) and Bolita (Bol). The color of the tortillas produced ranged from yellow-green to bluegreen. Ec tortillas were the only true blue type. Total anthocyanin content (TAC) varied between 3.67 and 1.11 mg equivalents of cyanidin 3-glucoside/kg dry weight (DW). Total soluble phenolics (TSP) were between 9.42 and 5.16 mg equivalents of gallic acid/kg DW. AA was highly correlated (p < 0.01) with TAC, but not with TSP. Blue Ec tortillas had the highest AA, and Bol tortillas had the lowest AA. Color parameters, TSP and TAC allowed the appropriate grouping of blue tortillas according to the maize race they belong to and were made from.Color, composición fenólica y actividad antioxidante de tortillas azules de razas mexicanas de maíz RESUMEN Los productos de cereales elaborados con granos pigmentados son atractivos para los consumidores. Se determinó la variabilidad en color, composición fenólica y actividad antioxidante (AA) de las tortillas azules de dieciocho variedades nativas de maíz con grano azul/púrpura de tres razas mexicanas: Chalqueño (Chal), Elotes cónicos (Ec) y Bolita (Bol). El color de las tortillas varió de amarillo-verdoso a azul verdoso; las de Ec fueron las únicas verdaderamente azules. El contenido total de antocianinas (TAC) varió entre 3,67 y 1,11 mg equivalentes de cianidina 3-glucósido/ kg muestra seca; los fenoles solubles totales (TSP) variaron de 9,42 a 5,16 mg equivalentes de ácido gálico/ kg muestra seca. El TAC fue altamente correlacionado con AA. Las tortillas de la raza Ec tuvieron la mayor AA. Las tortillas de la raza Bol tuvieron la AA más baja. Los parámetros de color, TSP y TAC permitieron agrupar de forma adecuada las tortillas azules según la raza a la que pertenecen. ARTICLE HISTORY

The maize produced in the highlands of Mexico (>2,400 masl) is generally not accepted by the flour and masa and tortilla industry. The objective of this work was to evaluate the grain quality and tortilla properties of maize landraces commonly grown in the highlands of Mexico and compare them with improved germplasm (hybrids). Germplasm analysis included 11 landraces, 32 white hybrids, and six yellow hybrids. Grain quality was analyzed for a range of physical and chemical factors, as well as for alkaline cooking quality. Landrace grains tended to be heterogeneous in terms of size, hardness and color. All landraces had soft-intermediate grains with an average flotation index (FI) of 61%. In contrast, hybrid grains were homogenous in size and color, and harder than landrace grains, with a FI of 38%. Protein, free sugars, oil and phenolic content in landraces were higher than in the hybrids. Significant correlations were found between phenolic content and tortilla color (r= -0.60; p<0.001). Three landraces were identified as appropriate for the masa and tortilla industry, while all the hybrids evaluated fulfilled the requirements of this industry.

En México cada año se importan 10 millones de toneladas de grano de maíz (Turrent, 2009), por lo que es urgente incrementar la producción y contar con variedades que presenten mayor productividad. En los Valles Altos de México, ubicados a más de 2200 msnm, en el año 2014 se cosecharon dos millones de hectáreas de maíz, obteniéndose un rendimiento promedio de 2.82 t ha-1 (Virgen-Vargas et al., 2016). Con la aplicación de recomendaciones tecnológicas y un mayor uso de variedades mejoradas se podrían elevar los rendimientos de maíz. En 300 mil hectáreas de Valles Altos, con humedad residual, punta de riego y buen temporal, donde el rendimiento promedio es de 3.5 t ha-1 de grano, se podrían sembrar híbridos que incrementarían el rendimiento a 6.0 t ha-1 (Tadeo-Robledo et al., 2016).

Se utilizaron granos de las variedades ‘V-229’ y ‘V-231A’ de maíz (Zea mays L.) para determinar sus propiedades físicas y químicas y su calidad para tortillas y botanas. La variedad ‘V-229’ produjo grano mediano de color crema, con textura intermedia y alto porcentaje de proteína (11.2 %), con 3.9, 0.29 y 0.07 % de aceite, lisina y triptofano, respectivamente; la humedad de su nixtamal fue de 39.6 % y la de sus tortillas de 41 %, con pérdida de sólidos de 3.2 % y una retención de pericarpio de 42.5 %, lo que significa que estos granos son apropiados para las industrias de la masa y la tortilla. La variedad ‘V-231A’ formó grano grande de color amarillo, con un índice de flotación de 37 % correspondiente a textura dura, con altos porcentajes de aceite (4.9 %) y proteína (11.9 %). Los altos contenidos de luteína (14.3 μg g-1) y de β-caroteno (5.22 μg g-1) de la ‘V231A’ indican que es una alternativa viable para mejorar la calidad nutricional de las tortillas y botanas, así como una excelente opción en la alimentación de aves.